A liquid crystal display device, especially an active matrix liquid crystal display device, has been widely used as a display element. According to this active matrix liquid crystal display device, picture elements include respective switching elements. In order to control the respective switching elements, a plurality of scanning signal lines and a plurality of video signal lines are provided so as to intersect each other. The respective switching elements are provided at respective intersections of the plurality of scanning signal lines and the plurality of video signal lines. Note that a substantially rectangular region defined by a scanning signal line and a video signal line is regarded as a picture element and the picture element includes a picture element electrode.
(Vertically-Lengthened Picture Element Electrode)
Note here that the picture element electrode has been vertically lengthened in general. The following description is given with reference to (a) of FIG. 16. (a) of FIG. 16 is a drawing illustrating an arrangement of picture elements 14 in a liquid crystal display device 10 which realizes color display.
In order to realize color display, three kinds of the picture elements 14 are provided so as to display R (red), G (green), and B (blue), respectively (see (a) of FIG. 16).
A single pixel 16 is constituted by a set of the three kinds of the picture elements 14 for R, G, and B.
Note here that the pixel 16 is substantially square in general at least for the purpose of displaying a more natural video picture to a viewer of the liquid crystal display device 10. The liquid crystal display device 10 often has a rectangular shape which is transversely lengthened. In view of this, each of the picture elements 14 has been vertically lengthened so that a larger number of the plurality of scanning signal lines or the plurality of video signal lines are drawn toward longer sides of the rectangular shape.
Specifically, the pixel 16 has been vertically partitioned into three, and each of the picture elements 14 for R, G, and B has been vertically lengthened. This provides a single pixel 16 with (i) three signal lines (video signal lines 35) in the vertical direction and (ii) a single signal line (a scanning signal line 32) in a transverse direction. As a result, the number of the signal lines (video signal lines 35) which are drawn toward the longer sides of the rectangular shape has been larger than that of the signal lines (scanning signal lines 32).
Note that a picture element electrode 60 is provided in a substantially entire region of the picture element 14. In view of this, the picture element electrode 60 has also been vertically lengthened in accordance with the picture element 14 which has been vertically lengthened as described earlier.
(Transversely-Lengthened Picture Element Electrode)
The following suggests an arrangement of a picture element 14 including a picture element electrode 60 which is transversely lengthened, in contrast to the picture element electrode 60 which is vertically lengthened as described earlier. Such an arrangement intends to reduce the number of video signal lines 35 so as to achieve a lower power consumption. The following description is given with reference to (b) of FIG. 16. (b) of FIG. 16 is a drawing illustrating, similarly to (a) of FIG. 16, an arrangement of the picture elements 14 in a liquid crystal display device 10 which realizes color display.
According to the liquid crystal display device 10 including the picture element electrodes 60 which are transversely lengthened, a single pixel 16 is partitioned into three not vertically but transversely (see (b) of FIG. 16). Then, three picture elements 14 which are transversely lengthened are provided in the single pixel 16. Note that the three picture elements 14 correspond to R, G, and B, respectively.
The picture element electrode 60 is also transversely lengthened in accordance with the picture element 14 which is transversely lengthened.
Employment of the arrangement causes an increase in number of the scanning signal lines 32 provided in the transverse direction to 3 (three), but allows a reduction in number of the video signal lines 35 provided in the vertical direction to 1 (one). This can reduce a driver for the video signal lines 35 which consumes more power and is higher in production cost in general than a driver for the scanning signal lines 32. This allows a lower power consumption and a production cost reduction.
Note that a circuit configuration of the driver for the scanning signal lines 32 is simpler than that of the driver for the video signal lines 35. In view of this, circuits of the respective drivers for the scanning signal lines 32 and the video signal lines 35 are provided, together with the scanning signal lines 32 and the video signal lines 35, on a single substrate, whereby a further reduction in production cost can be achieved.
Note again that the circuit configuration of the driver for the scanning signal lines 32 is simpler than that of the driver for the video signal lines 35. This allows (i) a reduction in region where the drivers are mounted and (ii) a contribution to miniaturization of the liquid crystal display device 10.
Note again that the circuit configuration of the driver for the scanning signal lines 32 is simpler than that of the driver for the video signal lines 35. In view of this, it is also easy to provide a single driver with the circuits of the respective drivers for the scanning signal lines 32 and the video signal lines 35. In this case, the number of the drivers can be reduced. This can contribute to (i) miniaturization of the liquid crystal display device 10 and (ii) a reduction in cost of mounting the drivers.
For example, Patent Literature 1 discloses a liquid crystal display device including transversely-lengthened picture element electrodes as mentioned above.
(Patent Literature 1)
Namely, in order to achieve a reduction in production cost and a lower power consumption, Patent Literature 1 discloses a liquid crystal display device including picture element electrodes which are lengthened in an extended direction of scanning signal lines.
Note here that in order to reduce a display defect such as a flicker, it is generally necessary that a parasitic capacitance generated between a picture element electrode and a scanning signal line which drives a picture element of the picture element electrode (this parasitic capacitance is hereinafter denoted as Cgd) be small with respect to a total of parasitic capacitances placed on the picture element electrode (this total is hereinafter denoted as Cpix). For example, when the scanning signal line is changed from an electric potential for turning ON the picture element electrode to one for turning OFF the picture element electrode, there occurs a change in electric potential of the picture element electrode in accordance with a ratio of Cgd to Cpix and a scale of the change in electric potential of the scanning signal line. In a case where AC driving is carried out for the prevention of deterioration in liquid crystal, a display abnormality such as a flicker or a luminance abnormality occurs if voltages applied to the liquid crystal are different between cases where (i) the picture element electrode has a positive electric potential with respect to a common electrode and (ii) the picture element electrode has a negative electric potential with respect to the common electrode. This requires the change in electric potential of the picture element electrode to be corrected by controlling a video signal or an electric potential of the common electrode. Note here that it is impossible to appropriately carry out the correction in a case where (i) the correction cannot be carried out for each tone, (ii) a range of correction values is narrow due to voltage limitation, or (iii) the correction can be carried out only in given (e.g., 50 mV) increments. This reduces allowance against a display defect and Cgd is therefore required to be as small as possible. Further, it is preferable that a liquid crystal capacitance included in Cpix and especially a storage capacitance be large. Note here that (i) the liquid crystal capacitance refers to a capacitance generated, via a liquid crystal material, between the picture element electrode and the common electrode and (ii) the storage capacitance refers to a capacitance juxtaposed to the liquid crystal capacitance.
As for this point, according to the arrangement disclosed in Patent Literature 1, a picture element electrode is extended beyond a scanning signal line, and a reduction in Cgd can be expected by shielding, with an adjacent picture element electrode, an electric field occurring toward a place where the liquid crystal material is sandwiched.
Patent Literature 1
Japanese Patent Application Publication, Tokukaihei, No. 11-167127 A (Publication Date: Jun. 22, 1999)